Coordination chemistry of N,N′-bis(coordinating group substituted)oxamides: a rational design of nuclearity tailored polynuclear complexes

A study of the exchange interaction through phenolato, oximato and oxamidato bridges in MnIICuII dimers. Crystal structure of [Cu(salen)Mn(hfa)2]

The crystal structures of [Cu(bipy)(3)][BPh(4)](2), 1, and [Zn(bipy)(3)][BPh(4)](2), have been determined at low temperature. 1 and 2 are closely related, but are not isostructural. Both contain a two-dimensional supramolecular construct (SC) involving a sandwich structure. 1 has a six-coordinate CuN(6) chromophore with a regular elongated octahedral stereochemistry and rhombic in-plane bond lengths. The associated tetragonality value, T, of 1 is 0.8868. 2 involves a six-coordinate octahedral chromophore. Differences between 1 and 2 relate to the tendency of copper(II) complexes to undergo a Jahn-Teller (JT) distortion. The zinc(II) cation feels solely the host site strain, whereas the copper(II) cation also involves vibronic JT type coupling. The copper polyhedron geometry is characterized by both phenomena, with the vibronic interaction dominating. Scatter plot analysis involving the tris-chelate copper(II) series suggests that neither pure Q(theta) or Q(epsilon) components or the a(2u) mode operate in isolation over the entire series. All three operate in combination with varying quantifiable contributions, leading to distortion from the regular tetragonal octahedral stereochemistry.

Structural systematics of the [Cu(chelate)3][Y]2 series. An interesting crystallographic structural insight involving vibronic coupling and the Jahn-Teller effect (JTE). The syntheses and low temperature crystal structures of tris(2,2'bipyridyl)copper(II) tetraphenylborate and tris(2,2'bipyridyl)zinc(II) tetraphenylborate.

N,N′-Bis(3-aminopropyl)oxamide (H2L1) which can adopt cis and trans conformations reacted with copper(II) salts in its deprotonated form to yield the compounds [CuL1]1, [Cu3L21(NO3)2]·H2O 2, [Cu2L1(NO3)2]3 and [Cu2L1(O2CMe)2]·2H2O 4. The structures of 1, 3 and 4 have been determined by single-crystal X-ray diffraction methods. That of 1 consists of mononuclear [CuL1] units where the oxamidate is in a cis conformation co-ordinated to the copper atom through its four nitrogen atoms. The copper surroundings are close to square planar. The amidate–copper bond distance [1.955(6)A] is significantly shorter than that involving the amine group [1.999(7)A]. The structures of 3 and 4 comprise centrosymmetric trans oxamidate-bridged copper(II) dinuclear units which are linked by asymmetric bis(monodenate) nitrate (3) and acetate (4) ligands to yield a sheet-like polymer (3) and an alternating chain (4). The co-ordination geometry around each copper atom is distorted square pyramidal: the equatorial plane comprises the oxygen and nitrogen atoms of the amide, the nitrogen atom of the amine group and an oxygen atom from nitrate (3) or acetate (4) ligands. The apical position is filled by an oxygen atom from another nitrate (3) or acetate (4) group. The copper–copper separations across the oxamidate are 5.190(1) and 5.244(1)A for 3 and 4, respectively, and those across the nitrato and acetato groups are 5.116(1) and 3.350(1)A. Variable-temperature magnetic susceptibility measurements show a Curie law behaviour for 1 and the occurrence of a strong antiferromagnetic coupling through the oxamidate bridge in 2–4(J=–325, –393 and –305 cm–1, respectively). The versatility of L1 as a ligand and its ability to mediate strong antiferromagnetic interactions is analysed and discussed.

Conformational change of the N,N′-bis(3-aminopropyl)oxamidate ligand in nuclearity tailoring copper(II) complexes

Tetra(μ3-hydroxo)hexa(μ2-carboxylato-O,O′)-bridged tetranuclear terbium(III) cubane complex

From the planar monomeric fragment Cu(oxpn) where oxpn is N, N′-bis(3-aminopropyl)oxamido, we have synthesized three complexes, namely[Cu(oxpn)Mn(bpy)2](ClO4)2H2O (1)(bpy = 2, 2′-bipyridyl), [Cu(oxpn)Mn(phen)2](ClO4)22H2O (2) (phen = 1, 10-phenanthroline), and [Cu(oxpn)Mn(NO2-phen)](ClO4)2H2O (3) (NO2-phen = 5-nitro-1, 10-phenanthroline) Based on IR, elemental analyses, electronic spectra and conductivity, the complexes are proposed to have an oxamido-bridged structure and consist of Cu(II) in a planar environment and Mn(II) in a distorted octahedron The complexes have been characterized by variable-temperature magnetic susceptibility (4-300 K) and the susceptibility data were least-squares fit to the susceptibility equation derived from the spin Hamiltonian including single-ion zero-field interaction for Mn(II) ion Ĥ = −2JS1-S2-DS2 z1, where D is the axial zero-field splitting parameter for the Mn(II) ion The exchange integral, J, was found to be equal to -1073 cm−1 in (1) -1520 cm−1 in 

Synthesis and Properties of μ-Oxamido Heterobinuclear Cu(II)-Mn(II) Complexes

X-ray crystal structure of Cu(bipy)3(ClO4)2

Two novel μ-oxamido heterotetranuclear complexes have been synthesized, namely Cu3Gd(oxpn)3(NO3)3 and Cu3Nd(oxpn)3(NO3)3 2H2O, where oxpn is N,N′-bis(3-aminopropyl)oxamide. The Complex Cu3Gd(oxpn)3(NO3)3 was characterized by variable temperature magnetic susceptibility (4–300K) studies. The magnetic susceptibility data was successfully simulated by the equation based on the Heisenberg model, H = −2J(Ŝ1 Ŝ0 + Ŝ2 Ŝ0 + Ŝ3 Ŝ0). The exchange integral, J. was found to be equal to −0.60 cm−1. This indicates a weak antiferromagnetic spin-exchange interactions beween the Cu(II) and the Gd(III) ions.

Synthesis and Magnetism of Novel μ-Oxamido Heterotetranuclear Complexes [Cu3 IILnIII] (Ln = Gd, Nd)

Two novel μ-oxamido heterotetranuclear complexes have been synthesized, namely CuaGd(oxdn)aCIO4)a · H2O and CuaHo(oxdn)a(CIO4)a, where oxdn is N,N′-bis(2-aminopropyl)oxamide. The complex CuaGd(oxdn)a(CIO4)a · H2O was characterized by variable temperature magnetic susceptibility (4 ∼ 300 K) studies. The magnetic susceptibility data was successfully simulated by the equation based on the Heisenberg model, Ĥ = −2J(Ŝ1 · Ŝo + Ŝ2 · Ŝo + Ŝa · Ŝo). The exchange integral, J. was found to be equal to −8.3 cm−1. This indicates weak antiferromagnetic spin-exchange interactions between the Cu(II) and the Gd(III) ions.

Zong-Ming Liu

Papers

Synthesis and Properties of μ-Oxamido Heterobinuclear Cu(II)-Mn(II) Complexes

X-ray crystal structure of Cu(bipy)3(ClO4)2

Synthesis and Magnetism of Novel μ-Oxamido Heterotetranuclear Complexes [Cu3 IILnIII] (Ln = Gd, Nd)

Synthesis and Magnetic Properties of Novel Heterotetranuclear Complexes [Cu8 IILnIII] Containing N,N′-bis(2-Aminopropyl)Oxamide (Ln = Gd, Ho)